Didier Lacoste I believe hates Ferre Gola for one reason:
He is not the main star coming from Maison Mere.
For Didier Lacoste, he looked to be the big star during the period of 1998 to 2001 before he went to Wenge Tonya Tonya with Adolphe Dominguez. He had so much promise and he did have some success and he could have been near Ferre but then he felt down and has not recovered since then. He sees Ferre remaining on top and it angers him so much.
That is the real reason why he refuses to collaborate with Ferre. Jealousy, simple as that.